ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
1 PH 8151-ENGINEERING PHYSICS
ENGINEERING PHYSICS
U
NIT II
WAVES AND FIBRE OPTICS
2.6.PLANE PROGRESSIVE WAVES AND ITS WAVE EQUATION
Definition:
A wave which travels continuously in a medium in the same direction without any
change in its amplitude is called a progressive wave or a travelling wave.
Explanation:
A Plane Progressive wave equation can be obtained to represent the displacement of a
vibrating particle in a medium through which a wave passes. Each particle of a progressive
wave executes simple harmonic motion of the same period and amplitude but differing in
phase from each other.
(i)
Displacement of Point O:
Let us assume that a progressive wave travels from the origin (O) along the x direction from
left to right (Fig.). The displacement of a particle at a given instant.
y = A sin ωt------(1)
Where, A is the Amplitude and ω is the angular frequency of the particle, it is given by
-----------(2)
Where, T is the time period, it is defined as the total time take by the particle to complete one
oscillation.
Sub eqn. (2) in (1), we get
------(3)
Fig 2.6.1. Plane progressive waves
(source:askiitians.com)
